Methods and apparatus in a variety of forms have so far been known to make hydrogen by reforming reactions. The practice with all these conventional methods and apparatus was, however, to derive a heat necessary for reforming reactions, simply from either the sensible heat of a gas burnt outside of the reforming reaction apparatus or a sensible heat generated by a heating medium. As a result, the sensible heat comes to be supplied through the wall surfaces of the reforming reaction apparatus. Not only does this require the apparatus as a whole to be large in size, but also its thermal efficiency is far from being well satisfactory. Furthermore, if a hydrocarbon is used as it typically is methane requiring a heating temperature of 700 to 750° C. for its reforming reactions, such an external heating system while requiring that the wall surfaces of the reforming reaction apparatus be externally heated at a temperature much higher than that temperature has required that they be heated at a temperature below 1000° C. because if the temperature of 1000° C. is exceeded, the material that makes up the wall surfaces tends to deteriorate.
In order to dissolve such inconveniences in the prior art, the present applicant has already proposed in Japanese Patent Application No. 2000-58483 an invention pertaining to an improved reforming reaction or reforming method and apparatus in which as a mixture gas of a hydrocarbon or aliphatic alcohol and water vapor is supplied and contacted with a reforming catalyst, a small amount of oxygen is mixed in the mixture gas of hydrocarbon or aliphatic alcohol and water vapor in an appropriate stage and an oxidation catalyst is added to the reforming catalyst to oxidize a part of the hydrocarbon or aliphatic alcohol and thereby to liberate a heat so that the quantity of heat required for the reforming reaction is internally supplied.
While if an example is taken of the case with a hydrocarbon a temperature of 700 to 750° C. is required to terminate the reforming reactions as an endothermic reaction, it has been found that the improved method in which heat is liberated by the oxidation reaction within a catalyst layer makes it possible to generate a sensible heat sufficient to maintain a temperature of 700 to 800° C. Thus, designed to internally generate the heat and thereby making it possible to maintain a temperature in the range necessary for the reforming reactions, the method makes it possible to render not only the apparatus markedly smaller in size but also the thermal efficiency much higher compared with the prior art that relies on the external heating.
The present invention is a further improvement over the invention mentioned above and is designed to further improve the thermal efficiency. And, it basically utilizes a technical idea found to improve the thermal efficiency of a burning type deodorizer as disclosed in JP 2000-257837 A (Japanese Patent Application No. H11-59652), and applies the idea to the method of making of hydrogen by reforming reactions to further improve the thermal efficiency in the process.
The present invention is also to provide an apparatus for implementing such a method, the apparatus not only being of an improved thermal efficiency but also being possibly made further smaller in its entire structure.